Handle collisions on multi-voice rests

[Danielku15]

Issues

Fixes #355

Proposed changes

1. Extends the layouting engine to register used Y-positions of given time positions. These positions are then considered in multi-voice scenarios to displace rests.
2. Remove correction parameter of y-calculations
3. Corrected improper/decentered placement of tab notes
4. Adjusted beaming for tab bar renderer to handle overlaps and collisions better
5. Ensure beam helpers for rests which fixes some tuplet issues.
6. Adjusted some tuplet renderings.

Checklist

• I consent that this change becomes part of alphaTab under it's current or any future open source license
• Added handling of collisions for rests
• Ensure more than 3 voices are placed properly
• Allow rests to be placed in the middle of two other voices
• Consider shifted rests in bar overflows
• Merge rests of same duration at same location
• Double check performance impact of new data caching
• Avoid collisions on tab-beaming
• Existing builds tests pass
• New tests were added

Further details

• This is a breaking change
• This change will require update of the documentation/website